Wireless Local Area Networks (WLANs) are being contemplated or are known. Such WLANs are typically supported by WLAN controllers or servers, which may alternatively be referred to as private branch exchanges (PBXs), enterprise or network servers or controllers. The PBX normally provides a control and switching function between the public switched telephone network (PSTN) and the WLAN and within the WLAN for communication units operating therein or users thereof. The WLAN can be an attractive and inexpensive alternative for typical voice services such as telephony or dispatch services and may provide additional amenities such as high-speed wireless Internet and Intranet access as well as other real-time applications that may be more specific to a given enterprise.
Wireless wide area networks (wireless WANs or WANs) such as conventional cellular telephone systems are also known. Such networks provide the advantage of wide area coverage but may not be economically attractive for routine access to wideband or high speed data capabilities, such as are required for certain Internet or Intranet applications. Nevertheless a communication unit that is operating on a WLAN may move beyond the effective service area for the WLAN and thus need support or services from a WAN. In situations, sometimes referred to as loosely coupled systems, e.g. the WAN is intercoupled to the WLAN only via the PSTN, a communication unit operating on the WAN can experience problems. Generally there is a bias for operating on the WLAN, if that service is available, given the economic and utility issues suggested above, however a handover of an ongoing call, particularly a handin, e.g. from the WAN to WLAN given the loosely coupled nature of these independent networks, can be problematic. This is particularly troublesome when the WLAN is large or complex with multiple sites and multiple network controllers.
While various solutions for handover have been proposed when the WLAN is managed and controlled by a single network controller these do not scale to situations where the network controller that should be used to effect a handover of an ongoing call can not be resolved. Therefore, a need exists for apparatus and methodologies to support routing of calls such that handover of the calls are facilitated, particularly in larger and more complex enterprise networks.